1. Field of the Invention
This invention relates to a post-ashing treating method for substrates. More particularly, the invention relates to a post-ashing treating method for substrates which exhibits an excellent performance in treating substrates having been dry-etched under strict conditions followed by ashing and also exerts favorable corrosion-inhibiting effects on various metallic wires and metallic layers. The present invention is appropriately applicable to the production of semiconductor devices such as Ics and LSIs as well as liquid-crystal panel devices.
2. Description of Relevant Art
Semiconductor devices such as ICs and LSIs as well as liquid-crystal panel devices are fabricated by a process comprising the following steps: forming a conductive metallic layer or an insulating layer such as an SiO.sub.2 film formed onto a substrate by chemical vapor deposition or other suitable techniques; applying a uniform photoresist layer over the metallic or insulating layer; selectively exposing the applied photoresist layer to light and developing the exposed layer to form a photoresist pattern; selectively etching the above-mentioned conductive metallic layer or insulating layer through the photoresist pattern as a mask pattern to form a fineline circuit; and stripping away the unwanted photoresist layer.
As the metallic layer, use may be made of various ones, for example, aluminum (Al), an aluminum alloy (Al alloy) such as aluminum-silicon (Al--Si), aluminum-copper (Al--Cu) or aluminum-silicon-copper (Al--Si--Cu); pure titanium (Ti); or a titanium alloy (Ti alloy) such as titanium nitride (TiN) or a titanium-tungsten system (TiW). One or more of such metallic layers are formed onto the substrate.
With the recent tendency toward high-density integrated circuits, dry etching enabling fine etching with a higher density has become the major means. Also, it has been a practice to employ plasma ashing, etc. to remove the unwanted photoresist layers after etching.
After the completion of these strict processing, resist residues such as modified photoresist films would adhere and remain in the side or bottom of patterns. It is also observed that metal depositions are formed in the step of etching metallic layers. It is, therefore, necessary to completely remove these residues, as there arises some problems, for example, a decrease in the yield of producing semiconductors.
These residues differ in composition from one another depending on the type of the etching gas employed, the ashing conditions, the type of the metallic layer(s) formed on the substrate, the type of the photoresist employed, etc. In recent years, attempts have been made to improve semiconductors by various methods. As a result, the treating conditions in each step become strict and a great variety of metals are employed therefor. Consequently, the residues and depositions become complicated, which make it difficult to identify the those compositions. Under these circumstances, no satisfactory treating liquid has been known so far. Among all, it is very difficult to completely remove residues of photoresists to which inorganic natures have been imparted by plasma gases.
As liquid compositions for treating these residues, Unexamined Published Japanese Patent Application No. 222,574/1996 has disclosed detergent compositions which comprise alcohols and quaternary ammonium hydroxides. Although these compositions can exert treating performance at a certain extent, there arises another problem that metallic layers are corroded away thereby.
The present inventors conducted intensive studies with a view to solving the above-mentioned problems. As a result, they found that these problems could be solved by treating substrates with treating liquid compositions containing lower alkyl quaternary ammonium salts, polyhydric alcohols and water in specified proportions. The present invention has been accomplished on the basis of this finding.